1. Technical Field
The present invention relates generally to digital wireless telecommunications and, more particularly, but not by way of limitation, to a method, apparatus and system for selecting, by a mobile station, of a Public Land Mobile Network (PLMN) from a plurality of PLMNs.
2. History of Related Art
One of the most widely-used digital wireless telecommunications standards is the Global System for Mobile communications (GSM) standard, developed by the European Telecommunications Standards Institute. The GSM standard utilizes time division multiple access (TDMA) techniques. A GSM-compliant wireless communication system includes a base station subsystem (BSS). The BSS typically includes a plurality of base transceiver stations (BTSs) for transmitting and receiving radio frequency (RF) signals from a subscriber's mobile station (MS) and at least one base station controller (BSC) for managing radio resource and routing signals to and from the BTSs.
A Universal Mobile Telephone Service (UMTS) standard employs recently developed wide-band code division multiple access (W-CDMA) techniques. A UMTS-compliant system typically comprises a core network (CN) and a UMTS Radio Access Network (URAN) that includes a ground-based portion. The ground-based portion of the radio access network (RAN) is often referred to as the UMTS Terrestrial Radio Access Network (UTRAN) and comprises a radio network controller (RNC) and a base station (BS), which have analogous functionality to the BSC and the BTS of a GSM network, respectively.
A Public Land Mobile Network (PLMN) area is a geographical area in which a particular operator provides mobile communication services to users. From any location within the PLMN area, the user may set up calls to another user of the same mobile network, or to a user of another mobile network. Existing standards require a mobile station (MS) to locate a best possible PLMN for serving the mobile station by measuring signal strengths of Broadcast Control Channels (BCCH) sent by the mobile network. In most current systems, a radio network controller (RNC) or base station controller (BSC) of a mobile network is connected to a single PLMN. Therefore, in such systems, the BCCH channels include information related to the single PLMN. However, in other systems, the RNC/BSC may instead be connected to a plurality of PLMNs. The BCCH channels may, therefore, include information related to the plurality of PLMNs.